Field of the Invention and Prior Art
There are many practical, down-to-earth problems in flowing a quantity of fluid into batches of the fluid. Presumably, there is the equivalence of a control valve which opens and shuts in a conduit of fluids as it flows to make up the batches. The fluid could be liquid food stuffs flowing into a cooking kettle for subsequent heat processing. The fluid could be milk flowed into shipping containers. The variety of fluids is endless. The reasons for the batches, and their sizes, are countless. One common denominator, in the way of a problem, is the closure of the valve in the fluid supply line, which has to be closed to essentially terminate the flow of fluid to the batch.
It is generally appreciated that the sudden closure of a fluid valve, particularly a liquid valve, will develop forces of great magnitude in the supply system. The hydraulic reaction from sudden valve closure can be most destructive and is desirably avoided.
The second problem is in operating the valve so that it does not overshoot the batch quantity. In effect, the valve must close with precision to give accuracy in the determination of the batch. The problem is how to develop a signal to the control valve, which will begin its closing a predetermined time prior to the completion of each batch or fluid supplied through it. The final signal can then be applied to the control valve with acceptable shock in the delivery system and repeatable accuracy in determining the quantity of the batch.
More specifically, the majority of the systems of supply are controlled by an electrical network. A flow measuring device in the supply conduit generates voltage pulses whose frequency represents the flow rate of the supplied fluid in the conduit. It is well established in the art to monitor these voltage pulses and shut the supply valve when the number of pulses in this train equals those representative of each batch. The desire, and the problem of the art, is to establish a signal for the valve, which will start its closure a predetermined number of pulses before the batch total is reached. To put it simply, an electrical system is desired, which will produce at least two control signals for fluid valves, the first signal to be generated a predetermined interval before the end of the batch to start valve closure and a second signal to precisely close the valve at the end of a batch.